It is well known that overall fuel efficiency in a multiple-cylinder internal combustion engine can be increased by selective deactivation of one or more of the engine valves, under certain engine load conditions.
For an overhead-cam engine, a known approach is to equip the hydraulic lash adjusters for those valvetrains with means whereby the roller finger followers (RFFs) may be rendered incapable of transferring the cyclic motion of engine cams into reciprocal motion of the associated valves. Such lash adjusters are known in the art as Deactivating Hydraulic Lash Adjusters (DHLAs).
A prior art DHLA includes a conventional hydraulic lash adjuster disposed in a plunger having a domed head for engaging the RFF. The plunger itself is slidably disposed in a pin housing containing the lock pins which in turn is slidably disposed in a DHLA body. The pin housing may be selectively latched and unlatched hydromechanically to the body by the selective engagement of a spring and pressurized engine oil on the lock pins.
During engine operation in valve deactivation mode, the lock pins are withdrawn from locking features, typically an annular groove, in the body, and the pin housing is reciprocally driven in oscillation by the socket end of the RFF which pivots on its opposite pad end on the immobile valve stem as the cam lobe acts on the RFF. The pin housing is returned during half the lost motion reciprocal cycle by lost motion springs disposed within the body.
In a prior art DHLA, the required lost motion displacement is significantly larger than that of a comparable Deactivating Hydraulic Valve Lifter (DHVL) counterpart and so the packaging length in an engine is necessarily longer than desired. Prior art DHLAs represent compromises between packaging length and the maximum oil pressure capability of the device.
What is needed in the art is a shorter deactivating hydraulic lash adjuster.
It is a principal object of the present invention to reduce the length of a DHLA.